Step 1: Use:
\[
\cos2x=\cos^2x-\sin^2x
\]
\[
\cos2x=(\cos x-\sin x)(\cos x+\sin x)
\]
Step 2: Therefore,
\[
\frac{\cos2x}{\sin x+\cos x}
=
\cos x-\sin x
\]
Step 3:
\[
\int_0^{\pi/2}(\cos x-\sin x)\,dx
\]
Step 4:
\[
=[\sin x+\cos x]_0^{\pi/2}
\]
\[
=(1+0)-(0+1)=0
\]
\[
\boxed{0}
\]